1. Field of the Invention
The present invention relates to turbine blades and gas turbines, and in particular, to a turbine blade suited for use as a vane and a blade of a turbine, as well as a gas turbine using the turbine blade.
2. Description of the Related Art
In general, high-temperature working fluid flows through turbine blades used in a gas turbine. Therefore, a technology for cooling the turbine blades with a structure to cool the turbine blades using cooling fluid is known (for example, see Japanese Unexamined Patent Application, Publication No. HEI 04-63901 and Japanese Unexamined Patent Application, Publication No. HEI 08-260901).
Japanese Unexamined Patent Application, Publication No. HEI 08-260901 discloses a technology for performing film cooling in which cooling fluid is blown out from film holes or a shower head film holes and performing pin fin cooling by forming a channel through which cooling fluid passes in the trailing edge of the blade and providing projecting pin fins in the channel.
Japanese Unexamined Patent Application, Publication No. HEI 08-260901 discloses a technology for performing film cooling in which cooling fluid is blown out from film holes or a shower head and performing pin fin cooling by forming a channel through which cooling fluid passes in the trailing edge of the blade and providing projecting pin fins in the channel.
In recent years, to improve the efficiency of gas turbines, increasing the temperature of working fluid flowing into the gas turbines, and to cope therewith, improving the cooling efficiency of turbine blades have been under consideration.
As a method for improving the cooling efficiency in cooling turbine blades, for example, for pin fin cooling, a method for improving the cooling efficiency by increasing the velocity of cooling fluid that passes through a region in which pin fins are provided (hereinafter referred to as a pin fin region) is generally known.
However, one problem with cooling the trailing edges of the blades by pin fin cooling is the difficulty in decreasing the cross-sectional area of a channel through which the cooling fluid flows.
That is, turbine blades are often manufactured by casting, and in such a case, the above-described channel is formed using a ceramic core. As described above, to decrease the cross-sectional area of the channel, it is necessary to decrease the cross-sectional area of the ceramic core. Decreasing the thickness of the ceramic core weakens the strength of the ceramic core. This has a problem of making the ceramic core prone to poor casting due to the breakage thereof etc., thus decreasing the manufacturability of the turbine blades.
As a result, there is also a limitation in decreasing the cross-sectional area of the channel, so that the cooling efficiency at the inlet of the pin fin region cannot be increased, thus decreasing the cooling efficiency in the entire pin fin region.
In particular, there is a problem of insufficient cooling efficiency at the inlet of the pin fin region because the velocity of the cooling fluid cannot be increased at the inlet of the pin fin region although it receives a high heat load from combustion gas.